1. Field
The present invention relates generally to communications, and more specifically to broadcast communications.
2. Background
Wireless communication systems have traditionally been used to carry voice traffic and low data rate non-voice traffic. Today there is an increasing demand for high data rate (HDR) packetized data services that are provided to one or more terminals at the same time. Examples of such high data rate (HDR) services can include multimedia traffic based on voice, audio and video data sources such as, radio broadcasts, television broadcasts, movies, and other types of audio or video content, such as, stock information and emergency information. One example of a HDR service is known as the Broadcast-Multicast Service (BCMCS) for cdma2000® networks. The BCMCS can allow optimization of the cdma2000® radio interface for delivery of BCMCS content stream(s) to one or more terminals in one or more regions of an operator's network. A network operator can control each BCMCS content stream with regard to accounting aspects, regions of the network where the BCMCS content streams are available to various users, and encryption of the content of Multicast IP Flow(s) to protect against unauthorized reception.
As traditional wireless communication systems are designed for voice communications, the extension to support data services introduces many challenges. Specifically, provision of uni-directional services, such as broadcast service where video and audio information is streamed to a subscriber, has a unique set of requirements and goals. Such services typically have large bandwidth requirements. As such, system designers seek to reduce transmission of overhead information. Additionally, specific information is needed to forward and/or access the broadcast transmissions, such as processing parameters and protocols. A problem exists in transmitting the broadcast-specific information while optimizing use of available bandwidth.
Origination stations, such as base stations (BS), can provide multimedia traffic services to destination stations, such as mobile stations (MS), by transmitting an information signal that is often organized into a plurality of packets. A packet includes an address to which the packet is to be delivered, data (or payload) and control elements that are arranged into a specific format. The packet is marked with a beginning and an end. The control elements may comprise, for example, a preamble and a quality metric that can include a cyclical redundancy check (CRC), parity bit(s), and other types of metrics. The packets are usually formatted into a message in accordance with a communication channel structure. The message travels between the origination station and the destination station, and can be affected by characteristics of the communication channel, such as, signal-to-noise ratio, fading, time variance, and other such characteristics. Such characteristics can affect the modulated signal differently in different communication channels.
To begin receiving a BCMCS content stream, each destination station typically attempts to register with an origination station within the network to set up a bearer path for receiving programs. For BCMC services, overhead messages from the origination station tell the destination stations whether a certain program is available and if so whether it is transmitting. This is typically done by having the network provide a start time and an end time to the destination stations (for each program) before the destination stations attempt to register. The destination stations then know whether a certain program is available and if so whether it is transmitting.
Users of many destination stations may attempt to register for the program at approximately the same time by sending a registration message to the origination station over the reverse link access channel (RACH). The RACH is a common channel used for communication of layer 3 and Medium Access Control (MAC) messages from the destination station to the base station. The destination station transmits on the RACH without explicit authorization by the base station. There can be one or more RACHs per frequency assignment, wherein different RACHs are distinguished by different long pseudorandom noise (PN) codes. Typically, each RACH is shared by multiple destination stations. For example, many users may wait and attempt to register for the program shortly before the program starts. If multiple users attempt to register for a program at approximately the same time, then there is a risk that the reverse link access channel (RACH) can become congested, and problems can occur at the origination station.
In a system with many users, the system may not be able to handle the registration of a large number of users at the same time since this may cause congestion in the network at the origination station. Therefore, there is a need for a techniques in a wireless communication system that reduce the likelihood of congestion at the origination station.